<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <script src="https://cdn.staticfile.org/react/16.4.0/umd/react.development.js"></script>
    <script src="https://cdn.staticfile.org/react-dom/16.4.0/umd/react-dom.development.js"></script>
    <script src="https://cdn.staticfile.org/babel-standalone/6.26.0/babel.min.js"></script>    
</head>
<body>
    <div id="app">

    </div>
    <script type="text/babel">
       class Hello extends React.Component{
           constructor(props){
               super(props);
               this.state={
                   msg:"hello world",
                   arr:[1,2,3]

               }
           }
           render(){
            // 1.列表渲染
            // 2.事件
               return (
                   <div>
                    {this.state.arr.map((item,index)=>{
                        return(<p key={index}>{item}</p>)
                    })}
                       <div onClick={this.handleClick}>{this.state.msg}</div>
                   </div>
                )
           }
        //    涉及到this关键字的指向问题
           handleClick=()=>{
               this.setState({
                   msg:"change"
               })
           }
       }
       ReactDOM.render(
           <Hello/>,
           document.getElementById("app")
           )
    </script>
</body>
</html>